Diseases & Conditions

E. coli

E. coli in your spinach salad or hamburger can make for a memorable meal — one that leaves you with severe, bloody diarrhea and abdominal cramps. The Escherichia coli (E. coli) group of bacteria include numerous strains. Most types of E. coli are harmless and normally live in the intestines of healthy people and animals. But a few nasty strains, such as E. coli O157:H7, can cause serious food-borne illness, commonly referred to as food poisoning.

Healthy adults usually recover from illness caused by E. coli O157:H7 within a week, but young children and older adults can develop a life-threatening form of kidney failure called hemolytic uremic syndrome (HUS). Antibiotic medications aren't used for this E. coli problem, because they can increase your risk of developing HUS.

In the United States, about 75,000 people each year become ill after being infected with E. coli O157:H7. You may be exposed to the bacteria from contaminated water or food — especially raw vegetables and undercooked ground beef. The best way to protect yourself from E. coli is to handle your food safely.

Signs and symptoms of E. coli O157:H7 infection typically begin three or four days after exposure to the bacteria, though you may become ill as soon as one day afterward to more than a week later. The main signs and symptoms are:

• Diarrhea, which may range from mild and watery to severe and bloody
• Abdominal cramping, pain or tenderness

You may have a low-grade fever or no fever. Some people experience nausea or vomiting. If your illness is caused by E. coli O157:H7, you may have 10 or more bowel movements a day, some consisting almost entirely of blood.

Among the many strains of E. coli, only a few trigger diarrhea. One group of E. coli — which includes O157:H7 — produces a powerful toxin that damages the lining of the small intestine, which can cause bloody diarrhea.

A different type of E. coli called enterotoxigenic E. coli is a leading cause of diarrhea in children in developing countries and is the culprit in many cases of traveler's diarrhea. This type has become an increasing source of food-borne illness in the United States and other developed nations. Enterotoxigenic E. coli bacteria are also spread in contaminated food — including raw fruits and vegetables, raw seafood and unpasteurized dairy products — and in contaminated water.

How the bacteria spread
You develop an E. coli infection when you accidentally ingest the bacteria. Potential sources of exposure to contaminated animal or human fecal matter include:

• Contaminated food. Most cases of E. coli O157:H7 have been linked to undercooked ground beef. But nearly one-quarter of outbreaks stem from contaminated produce, including spinach, lettuce, cabbage, sprouts and tomatoes. Prepackaged vegetables and salad mixes may present a particular risk. The bacteria can also contaminate raw fruits, such as melons.

  Meat can become contaminated when cattle are slaughtered and processed. Most beef in the United States is produced in industrial feedlots, where large numbers of cattle are raised in close quarters. Ground beef combines meat from hundreds or even thousands of different animals, increasing the risk of contamination.

  Industrial farming also generates lagoons of liquid manure, which may spill into nearby streams. Runoff from feedlots can contaminate vegetable fields and orchards.

  E. coli bacteria also can spread from one surface to another, which means that bacteria on a cow's udder or on equipment can end up in milk. Pasteurization kills the bacteria, but raw milk can be a source of infection. Other foods that may become contaminated with E. coli include dry-cured sausage, salami and unpasteurized apple juice and apple cider.

• Contaminated water. Runoff from feedlots may pollute ground and surface water, including streams, rivers, lakes and water used to irrigate crops. Drinking or inadvertently swallowing untreated water from lakes and streams can cause infection. Although public water systems use chlorine, ultraviolet light or ozone to kill E. coli, some outbreaks have been linked to contaminated municipal water supplies. Private wells are a greater cause for concern. Some people have been infected after swimming in pools or lakes contaminated with feces.
• Person-to-person contact. E. coli bacteria can easily travel from person to person, especially when infected adults and children don't wash their hands properly. Family members of young children with E. coli infection are especially likely to become sick themselves. Children can shed the bacteria in their stools for up to two weeks after symptoms improve.

Outbreaks have also occurred among children visiting petting zoos and in animal barns at county fairs.

If you become ill after eating fresh produce or ground beef, or if you have severe or persistent diarrhea, contact your doctor promptly. Your doctor may test a stool sample for E. coli bacteria. Most E. coli infections — even those caused by O157:H7 — clear up on their own. But if you're at high risk of HUS, see your doctor at the first sign of profuse or bloody diarrhea.

To diagnose illness caused by E. coli infection, your doctor will send a sample of your stool to a laboratory to test for the presence of E. coli bacteria. The bacteria may be cultured to confirm the diagnosis and identify specific toxins, such as those produced by E. coli O157:H7. Researchers have also done genetic testing of E. coli bacteria to help determine if an infected person is at risk of developing HUS.

Most healthy adults recover from E. coli illness within a week. But some people — particularly young children and older adults — may develop hemolytic uremic syndrome (HUS). In this syndrome, bacterial toxins enter the bloodstream and start to destroy red blood cells. The damaged cells clog the tiny blood vessels in the kidneys, sometimes leading to kidney failure. HUS is the most common cause of acute kidney failure in children.

About 3 percent to 15 percent of people infected with E. coli O157:H7 develop HUS. The syndrome occurs most commonly in young children. Taking anti-diarrheal medications or antibiotics increases your risk of developing HUS, because toxins from the bacteria stay in your system longer.

Signs and symptoms of HUS include paleness, irritability, weakness, fatigue, low or no urine output, red urine and bruising. Most children recover completely from HUS with no permanent damage. But even with the best of care, including kidney dialysis, a few children die every year of HUS. Others may have lifelong kidney problems or other complications.

For illness caused by E. coli O157:H7, no current treatments can cure the infection, relieve symptoms or prevent complications. For most people, the best option is to rest and drink plenty of fluids to help with dehydration and fatigue. Avoid taking an anti-diarrheal medication — this slows your digestive system down, preventing your body from getting rid of the toxins.